502 Invasive Stink Bugs and Related Species (Pentatomoidea)
or taxonomic position of a species has been detected. In other words, if sufficiently studied, any combi-
nation of type and form of diapause can be found in any taxon within the Pentatomoidea.
The form of diapause (i.e., obligate or facultative) usually is considered a species-specific character
in Heteroptera. However, biological diversity virtually is unlimited and, in some cases, when different
populations of a species were studied, examples of intraspecific variation of diapause form and mecha-
nisms of voltinism control have been reported (Hodek 1977). Thus, within one species with a wide range
in the Northern Hemisphere, a tendency to enter diapause was much stronger in the northern popula-
tions with all bugs of these populations sometimes demonstrating obligate diapause. Closer to the range
core in the Temperate Zone, populations were heterogeneous with some individuals having obligate and
others having facultative diapause. Further south, most populations have facultative diapause or show a
strong tendency towards homodynamic seasonal development (nondiapause development in any sea-
son and nonstop sequence of generations without any pronounced period of seasonal dormancy). It is
likely that day length is less important in winter diapause induction as well as winter diapause, itself,
because it is less ecologically important in the (sub)tropic populations of true bugs than in populations
in the more temperate or cold climates. These tendencies have been demonstrated in the pentatomids
Euthyrhynchus floridanus (Mead 1976, Richman and Whitcomb 1978) and Podisus maculiventris (De
Clercq and Degheele 1993) in Florida (USA).
11.2.4 Two Seasonal Classes of Diapause: Winter and Summer Diapause
Insect diapause often is associated with winter and, in these cases, is called winter diapause, or hiber-
nation. Such examples have been documented in thousands of species from all major insect orders
(Danilevsky 1961, Saunders 1976, Tauber et al. 1986, Danks 1987). However, diapause as a special physi-
ological state can take place during other times of the year too. Frequently, insects can enter facultative
or obligate diapause in summer; in this case, such diapause is called summer diapause, or estivation. It
is important to understand that in some species, even one individual can have two different diapauses at
two different ontogenetic stages. This is the case, for example, in the pentatomid Picromerus bidens: this
predatory species passes winter in the state of obligate winter embryonic diapause and then adults may
enter facultative summer adult diapause (Musolin and Saulich 2000; see Chapter 12).
The ecological importance of dormancy during summer might be related to survival of extremely high
temperatures and dry conditions. In some other cases, summer diapause also is important for survival
during a rainy season or a period when food is too scarce. Finally, similarly to winter diapause, summer
diapause may be important for fine synchronization of the species’ seasonal cycle with local environ-
mental conditions (see Chapter 12). Summer diapause in Heteroptera has been studied much less than
winter diapause (Saulich and Musolin 2007b), and some interesting cases will be discussed in Section
11.8. However, in this chapter, we will concentrate mostly on winter diapause.
11.2.5 Diversity of Winter Diapause Patterns in Pentatomoidea
Among 82 species of Pentatomoidea in which seasonal development and/or winter dormancy have
been studied at least to some extent, most species (67, or ≈82%) overwinter as adults (Tables 11.1
and 11.2). In five families (i.e., Acanthosomatidae, Cydnidae, Parastrachiidae, Thaumastocoridae, and
Thyreocoridae) only adult diapause has been reported so far. Three species (i.e., Picromerus bidens,
Apoecilus [= Apateticus] cynicus, and Trochiscocoris hemipterus) overwinter in the embryonic stage
and all belong to Pentatomidae. In nine species, nymphs overwinter; among them, two species belong to
Pentatomidae (Carbula humerigera and Pentatoma rufipes), two to Plataspidae (Coptosoma mucrona-
tum and Coptosoma scutellatum), four to Scutelleridae (Odontoscelis dorsalis, Odontoscelis fuliginosa,
Odontoscelis lineola, and Poecilocoris lewisi) and one to Tessaratomidae (Musgraveia sulciventris).
Among all these species, only in P. lewisi and M. sulciventris does diapause appear to be strongly linked
to a particular nymphal instar (fifth instar in P. lewisi [Tanaka et al. 2002] and second instar, before the
commencement of feeding, in M. sulciventris [Cant et al. 1996]). In all other cases, nymphs of different
instars can overwinter: second through third/fourth instars do this more often than fifth instars; there are
no records so far of winter diapause in the first instar in Pentatomoidea (see Table 11.2 for references).